This means that there is something wrong on the SPI interface between the Yun Shield and the Arduino Board. There are two possible:

This means that there is something wrong on the SPI interface between the Yun Shield and the Arduino Board. There are two possible:

* User doesn't power the Yun Shield properly. [[http://wiki.dragino.com/index.php?title=Yun_Shield#Power_Requirement|Check this link for how to power it right]]

* User doesn't power the Yun Shield properly. [[Yun_Shield#Power_Requirement|Check this link for how to power it right]]

* Please check if the SPI connection between them is clean and doesn't have other components hooked onto it. Some components may interfere with the SPI connection.  

* Please check if the SPI connection between them is clean and doesn't have other components hooked onto it. Some components may interfere with the SPI connection.